Gas turbine engines generally include a compressor for compressing an incoming airflow. The airflow is mixed with fuel and ignited in a combustor for generating hot combustion gases. The combustion gases in turn flow to a turbine. The turbine extracts energy from the gases for driving a shaft. The shaft powers the compressor and generally another element such as an electrical generator. The exhaust emissions from the combustion gases generally are a concern and may be subject to mandated limits. Certain types of gas turbine engines are designed for low exhaust emissions operation, and in particular, for low NOx (nitrogen oxides) operation with minimal combustion dynamics, ample auto-ignition, and flame holding margins.
Low NOx combustors are typically in a form of a number of burner cans circumferentially adjoining each other around the circumference of the engine. Each burner may have one or more swirlers positioned therein. The swirlers may have a number of circumferentially spaced apart vanes for swirling and mixing the compressed airflow and the fuel as they pass therethrough.
One issue with known swirlers is that the gas flow therethrough may be unbalanced among the several vanes. A flow imbalance may cause uneven burning. Such uneven burning may result in an increase in emissions and possibly combustion dynamics. Rather, the goal is to promote a homogeneous flow through the swirlers so as to provide a sufficient combustion process while producing fewer emissions.
There is a desire, therefore, for a gas turbine engine with improved fuel/air mixing and, in particular, improved flow through the swirlers.